Contents

Introduction

Megalink is designed according to the ISO 3309 standard, providing you with Point-to-point serial communication links, using HDLC protocol. It can operate in half or full duplex mode on point-to-point line. Multidrop requires external equipment.

Megalink may operate up to 983 Kbaud in a high throughput mode where retransmissions are avoided. This is achieved by using a busy line (requires an extra pair of wires in each direction in addition to the X.21 defined lines. This mode is easiest using a Megalink to Megalink computer link. Operation without busy lines is possible below 307 Kbaud.

It is recommended that the Megalink interface have the highest priority.

Switches and indicators

This card has three thumbwheel switches, from the top of the card

TH1 - baud rate selection

0 - 307.2 kbps

3 - 1.2 kbps

6 - 9.6 kbps

7 - 38.4 kbps

8 - 153.6 kbps

9 - 76.8 kbps

11 - 19.2 kbps

13 - 4.8 kbps

14 - 2.4 kbps

settings not specified overlap with the specified settings. Baud rate selection is only relevant if the source oscillator switches are set to "baud rate via TH1".

Connectors

I/O Devices on the card

Modem connection

Programming

The Megalink DMA is operated by placing control information in a buffer memory, and the writing the address of this buffer - the LIST POINTER - to the Megalink module together with one of eight commands. The module will then perform the proper action. A command must be completed before a new command is issued. The only exception is the Device Clear sequences which may be initiated any time.